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UNDERGROUND ELECTRIC CABLE. No. 430,297. Patented June 17, 1890..

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Patented June 17, 1890.

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UNDERGROUND ELECTRIC CABLE.

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WILLIAM R. PATTERSON, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERNELECTRIC COMPANY, OF SAME PLACE.y

UNDERGROUND ELECTRIC CABLE.

y SPECIFICATION forming part of Letters Patent No. 430,297, dated J une17, 1890.

Application filed May 14, 1889.

To all whom. it may concern: Y

Be it known that I, WILLIAM R. PATTER- SON, a citizen of the UnitedStates, residing at Chicago, in the county of Cook and State ofIllinois, have invented a certain new and useful Improvement inUnderground Electric Cables, (Case 81,) of which the following is afull, clear, concise, and exact description, reference being had to theaccompanying drawxo ings, forming a part of this specification.

My invention relates to electric cables; and its object is to reduce thestatic capacity of such cables and make it possible or convenient toremove the core or the greater portion sired. Portions of the cable, asthose nearest the man-holes, are filled with an insulating substance toform a dam to prevent water from penetrating longitudinally. The cenzotral portions of each section-that is to say, the portions between theman-holes-except the portions in close proximity to the manholes, areleft with a dry core-that is to say, without insulating-filling-fsimplyinclosed in 2'5 the lead pipe. It will be understood that the pipe isnot liable to mechanical injury, eX- cept vin the man-holes, andtherefore it is only necessary to guard against the absorption ofmoisture by the core near the man-holes.

As to the state of the art prior to my invention, reference is made tomy patent, No. 378,175, granted February 21, 1888.

My invention will be readily understood by reference to the accompanyingdrawings, in which 1 Figure 1 is a View showing the preferable manner otfilling the two ends of a section with insulating-filling, the gas orair between the filled ends being compressed in the oper- 40 ation. Fig.2 is a View showing four sections of such cable spliced together, thesplices being so arranged as to come each at a different man-hole of theconduit. Fig. 3 is a longitudinal sectional view of my cable, showingthe core saturated and unsaturated or dry at alternate sections thereof.Fig. 4 is a transverse sectional view upon line fr, showing the coresaturated. Fig. 5 is a sectional view upon line y y, showing the coreunsaturated.

It will be understood that the core a is first deprived of moisture anddrawn into the lead pipe b.

Serial No. 310,752. (No model.)

The section may be, say, four hundred feet long. Insulating-flling,preferably paraffine, is then forced into the two ends of the section inany suitable manner. The apparatus shown in' Fig. 1 is adapted to dothis work, though I do not wish to limit this patent to any particularmethod or particular apparatus for forcing the insulatingfilling intothe ends of the section. The sections of 6o the desired length are thusmade and filled at each end with an insulating-filling as far as may bethought necessary. I prefer to fill each end of the section for adistance of about twenty-five feet, in order that there may be plenty ofmargin for splicing and plenty of length through which the moisture mustpenetrate slowly, so as to give due notice of the fault in case ofmechanical injury to the pipe at a man-hole. Thus, as shown in Fig. 2,the 7o, sections c d e f are spliced together'to form a single cable ofinsulated conductors. This cable, as a whole, is made up of the portionsbetween the man'holes containing the dry core and gas or air underpressure. Thesections at the man-holes are filled with insulatingmaterial like paraffine, in order that moisture may not penetratelongitudinallyin case of mechanical injury to the pipe at the man-holes.The vertical scale of the draw- 8o ings, Fig. 2, is much greater thanthe longitudinal. ,lt may be assumed that the depth of the man-holes issix feet and the longitudinal distance between them, respectively, fourhundred feet. Of course the length and depth may be varied ascircumstances may requi1e--as, forexample, the length of the blocks andthe grade-a man-hole being usually required at each street intersection.As shown in Fig. 8, the portions gof the cable are shown 9o with thecore saturated. The intermediate portions h 7L are left unsaturated.Thus a transverse section through any saturated portion g would appear,as shown in Fig. 4, while a section through the unsaturated portion 7i95 would appear, as in Fig. 5.

My cable as thus Inade will be of very low capacity since the greaterportion of the core will be left dry, the gas or air being of lowerspecific inductive capacity than liquid or solid Ioo insulatingsubstances of any kind. In case of injury to the pipe necessitating therenioval of a section of the cable, the core being for the greater partof its length loose in the pipe, may be readily removed. The core canthus be more readily utilized for electrical purposes.

Having thus described my invention, I claim as new and desire to secureby Letters Patent* l. A cable consisting of a lead pipe and a core ofinsulated conductors inclosed therein, said core being left dry inalternate sections, the portions of the cable between the dry sectionsbeing lled with solid insulating material and the dry sectionscontaining gas or air under pressure.

2. The combination, with a telegraph-cable consisting of a core ofinsulated conductors contained in a lead pipe, of a conduit in whichsaid cable is laid, said conduit being provided with man-holes, thecable at the man-holes being filled with an insulating substance whichsaturates the core, the intermediate portions of the cable being leftwith the core loose in the pipe, and gas or air under pressure beingcontained therein, substantially as and for the purpose specified.

3. A section of telegraph-cable filled at each end with an insulatingsubstance, the portion of the cable between said filled ends containingair or gas held under pressure by the insulating-filling, substantiallyas described.

In Witness whereof I hereunto subscribe my name this 11th day of May, A.D. 1889.

lVILLIAlNI R. PATTERSON.

Witnesses:

GEORGE P. BARTON, C. G. HAWLEY.

